The objective of this research program is to localize at the electron microscope level certain carbohydrate-containing macromolecules on developing photoreceptor synaptic membranes in the chick retina. We will be looking specifically at how these cell surface carbohydrates become more or less accessible to the EM labeling technique during photoreceptor synapse formation and after synaptic maturation. Carbohydrates on developing synaptic membranes will be visualized by the use of lectins which bind to certain sugar residues, in combination with peroxidase labeling techniques to visualize the actual sites of lectin binding. A further characterization of the chemical nature of developing synaptic membrane carbohydrates will be obtained by testing the effects of prior proteolytic and glycolytic digestion on the lectin staining. The nature of the protein moiety of glycoprotein carbohydrates will be investigated by the use of polyacrylamide gel electrophoresis in combination with specific lectin-peroxidase stains. These glycoproteins will be extracted from the gels and immunocytochemical techniques will be used to localize the individual glycoproteins in tissue sections.